Two stage thermostat



June 1942' c. G. KRONMILLER 2,285,445

TWO 8 TAGE THERMOSTAT Filed Nov. 22, 1939 inventor Carl G. Kvonmiller Patented June 9, 1942 UNITED STATES PATENT OFFICE Application November 22. 1939, Serial No. 305,648

l'lchims.

This invention relates broadly to automatic; switches, and is more particularly directed to a condition responsive switching mechanism for providing a two stage action.

The copending application of Albert E. Baak,

Serial No. 303,953, filed November 13, 1939, shows a. two stage switching mechanism in which an armature is rotatably carried by a condition responsive element (a bimetallic thermostat in this particular case) and in which this armature cooperates with a pair of permanent magnets, the two stage action being accomplished by placing one of the magnets closer to the point about which the armature rotates than the other. A

stationary contact is placed adjacent each magnet and cooperating movable contacts are carried by the armature. In this manner the stationary contact which is adjacent the magnet farthest from the axis of rotation of the armature is made first and broken last because its 0 -magnet .is operating through a longer lever arm and. therefore exerts agreater effective force on the amiature than the other.

It is an object of the present invention to change the above constructionin order to im prove the contact action and reduce the diiferential between the two switch actions.

A further object is to mount the armature on the bimetallic element by means of a pivotal connection whereby. a-freer action of the armature by the bimetallic element.

A still further object is to use a signal magnet and have one end attract one end of the armature and the other end attract the other end of the armature.

These and other objects will readily become apparent as the following specification is read in the light of the accompanying drawing, in which Figure l is a view in elevation showing a preferred embodiment of my invention,

cause a rotation of the bracket l8.

The plate l5 carria an axle on which the bracket I8 is pivotally mounted, it being retamed thereon by means of the screw [9. The bracket II is provided with an upwardly extending arm 2| whose end is bifurcated to form the fingers 2|. A second arm 22 is pivotally mounted on the same axle with the bracket II and this arm'22 is provided with an extension 23 which carries an eccentric screw 24 extending between the fingers 21. The upper end of the arm; 22 is also bifurcated to form the fingers which receive the pin 21 on the upper end of the adjusting lever 2' which is pivoted as shown at 29 to an extension on the plate 15.

It can be seen that movement of the lower end of the adiusting lever 28 back and forth will cause it to rotate about the point 29 and cause a slight movement of the pin 21 which will in turn rotate the arm 22 and hence move the eccentric 24. .Movementof the eccentric 24 will The bracket l! is connected to one end of a bimetallic thermostat 3|. Therefore movement of the adjusting lever 28 will rotate the thermostat 3| and cause an adjustment thereof. The lower end of the lever 2! is provided with amarker 32 which cooperates with a scale 33 on the lower end of the plate 15 to indicate the temperature to which the thermostat 31 has been set. A screw 34 extends through an arcuate slot 35 L in the plate ii and enters a tapped hole in lever 28. In this manner the lever 28 can be moved to any desired position and then can be locked in this position merely by tightening the screw 3|; It will be obvious that by rotating the eccentric 24 the angular relationship between the bracket ll and the arm 22 can be changed in order to calibrate the thermostat with respect to the scale 33.

The free end of the bimetallic thermostat 3| carries an insulating member 31 which in turn pivotally supports the armature 38 by means of the Pi 39. The armature carries onset portions ll and ll which act as stops for the press-back Figure 2 is a detailview of the contact con- 5 blades R and 43 .Which carry e movable struction, and Figure 3 is a detail view of the channel shaped magnet.

Referring to Figure 1 of the drawing the feierence numeral H indicates a subbase by means of which the two stage thermostat is mounted on a wall or other flat surface. An insulating base I2 is connectedto the subbase II by means of the screws 13. The subbase I2 is provided with a channel portion ll adapted to house the adjusting mechanism for the thermostat. A metallic plate [5 is fastened to the'base [2 by means of the screws it which enter the plate l5 from the reverse side of the base l2. The plate l5 tacts ll and 45. These pressback blades are mounted (in tongues l6 which are struck from the armature II and can be bent to adjust the tension in the pressback blades to the proper value. The armature 38 is provided with a pair of ilchaped magnetic pieces I! which cooperate with the ends of a channel shaped permanent magnet 4!. The magnet 4 is mounted on bracket 5. by means of screws il.

Bracket 52- adjustably carries the stationary contact 53 which extends through the legs of the U-shaped magnetic piece I to cooperate with the contact 44. The bracket 52 also adjustably carries the insulated stop 55 which engages covers the lower end of the channel portion H. the offset portion ll of the armature 38 to limit the movement of this armature away from the magnet 49. A metal piece It is connected to the magnet 49 and adjustably carries a stationary contact I! which cooperates with the movable contact 45. The insulating member 31' adjustably carries screw 58 which cooperates with the onset portion 4| oi the armature 3! to limit the movement of the armature away from the magnet 49. It will be noted that the pivot pin 39 for the armature 38 is closer to the lower end of the magnet than to the upper end of the magnet and that the armature 39 is unbalanced. That is, its upper end is longer than the lower end with the 7 result that the upper end of the magnet 49 oper ates on the armature 38 through a longer lever arm than the lower end of the magnet and hence will first attract the magnetic piece 48 to pull the contact 44 into engagement with the stationary contact II and the pressback blade 42 will be pressed vback until it engages the oflset portion 4| or. the armature ll. On a further decrease in temperature the thermostat II will "move again toward the left and the lower end of the magnet 4! will attract the lower magnetic piece '48 to move the contact 45 into engagement with the stationary contact 81. On an increase in temperature the free end of the thermostat will move toward the right and first pull the lower end or the armature SI away from the magnet 49 and into engagement with the screw ll. A further increase in temperature will result in the movement of the upper end of the armature to the and 53. i

Adjustment of the differential of thh switching mechanism maybe accomplished by adjusting the stationary contacts 53 and 51 to vary the gap between the magnetic pieces 48 and the permanent magnet 49 when both switches are closed.

A further adjustment is provided by means of the stops 5! and 58 to adjust the distance which the armature II can move away from, the permanent magnet 49.

It will be appreciated that two separate magnets may be used instead of the single magnet 49. If this were desired one magnet would be the m, I wish it to'be understood that I ammbe limited by the scope of the appended claims rather than by the specific embodiment disclosed. I claim as my invention: 7 lrln a device of the character described, an armature, a substantially frictionless pivot for said armature about which it is adapted to ro-' tate, magnetic means cooperating with said armature at spaced points, said pivot, being nearer one of said points than the other, so that said magnetic means will exert relatively difierent rotative forces on said armature at said points, and means for moving said pivot toward and away from said magnetic means.

2. In a device of the character described, an armature, a substantially frictionless pivot for said armature about which it is adapted to rotate, magnetic means cooperating with said armature at spaced Points, stationary contacts adjacent said points, movable contacts carried by said armature, said pivot being nearer one of said points than the other, so that said magnetic means will exert relatively different rotative forces on said armature at said points, and means ior'moving said pivot toward and away from said magnetic means whereby certain of said contacts will always make before the others, and said others will always be the first to break. 3. In a device of the characterdescribed, an armature, a pivot for said armature about which it is adapted to rotate, magnetic means cooperating with said armature at spaced points, stationary contacts adjacent said points, movable contacts carried by said armature, said pivot being nearer one oi said points than the other, means for moving said pivot toward and away from said magnetic means whereby certain of said contacts will always make before the others,

and said others will always be the first to break,

right separating the contacts 44 5 placed adjacent contact 53 to attract the upper end of the armature 38 and a second magnet would be located adjacent the contact 51 to attract the lower end of the armature 38. .This arrangement would work just as well as with the single magnet. However, the single magnet is chosenas the preferred embodiment of the invention so that any variation in the magnetic strength of the magnet cannot change the se-. quence of switch operation. If two magnets were used and the magnet, adjacent the contact 53 were to become considerably weaker than the magnet adjacent the contact 51, the switch action would be reversed so that the lower end of V the armaiaire would pull in before the upper end.

As various changes and modifications of this inventionmayoccurtothosewhoareskilledin ating with-said armature engagement of said contacts limiting the movement of said armature toward said magnetic means, and means for adjusting said stationary contacts for varying the air gap between-said armature and said magnetic means when said contacts are made.

4. In a device of the character described, an armature, a pivot for said armature about which it is adapted to rotate, magnetic means cooperating with said armature at spaced points, stationary contacts adjacent said points, movable contacts carried by said armature, said pivot being nearer one of said points than the other, means for moving said pivot toward and away from said magnetic means whereby certain of said contacts will always make before the others,

, and said others will always be the first to break,

and stops for limiting the movement of each of Said points away from said magnetic means.

5. In a deviceof the character described, an armature, a pivot for said armature about which it is adapted to rotate, magnetic means cooperat spaced points, stationary contacts adjacent said points, movable contacts carried by said armature, said pivot.

being nearer one vof said points than the other, means for moving said pivot toward and away from said magnetic means whereby certain of said contacts will always make before the others,

and said others will always be the first to break,

engagement of said contacts limiting the movement of said armature toward said magnetic means, and means for adjusting said stationary contacts for varying the air gap between said armature and said magnetic means when said contacts are made, and adjustable stops for an i. second stops limitm with a predetermined always M o l i etaliic 1 id sale. end always fore said other end ena by the free end or the eiemen; by means 01 a :ireely pivoted connection an in ermediate point on said arm, first and second movable contacts carried by said arm at opposit-e sides oi sail pivotai connection, first and second stationary contacts for engagement by said first and second movable contacts respectively on movement of said arm in one direction, stops for limiting movement of said arm in the opposite direction, means biasing said first contacts into engagement with a predetermined force and biasing said second contacts into en-- gagement with a predetermined lesser force whereby said first contacts always make first and break last, and means for moving the fixed end of said bimetallic element to vary the temperature at which said contacts are made and broken.

8. In a device of the character described, a bi metallic element having a fixed end and a. free end, an armature carried by the free end of the element by means of a pivotal connection intermediate the ends of said armature, magnetic means attracting said armature at first and second points on opposite sides of said pivotal connection, one of said points being nearer said connection than the other, and means for limiting the movement 0! said armature in each direction.

9. In a. device of the character described, a bimetallic element having a fixed end and a free end, an armature carried by the free end of the element by means of a pivotal connection intermediate the ends of said armature, a pair of movable contacts carried by said armature at opposite sides of said pivotal connection, stationary contacts cooperating therewith, magnetic means tending to hold one pair of contacts in engagement with a greater force than the other pair; and stops limiting the movement of both ends of said armature away from said stationary contacts, one or said'stops being carried by said bimetallic element.

10. In a device of the character described, a. bimetallic element having a fixed end and a free end, an armature carried by the free end of the element by means of a pivotal connection intermediate the ends or said armature, a magnet. one end of said magnet attracting said armature at a point on one side of said pivotal connection, the other end of said magnet attracting said armature at a point on the other side of said pivotal connection, one of said points being nearer the pivotal connections than the other, and means iimitirig the movement of said armature away from said magnet.

ll. in a device of the character described, a bimetallic element having a fixed end and a free end, an armature carried by the free end of the element by means or a pivotal connection in. termediate he ends of said armature, a chamnel shaped permanent magnet extending longitudinaily of and adjacent said armature, pivotal. connection being nearer one end of said magnet than the other, and means b'niiting the movement of armature away from. said magnet.

l2. a device oi the character described, a bimetallic element having a fixed end and a free end, an armature carried by the free end oi the element by means of a pivotal connection intermediate the ends or said armature, a. pair of movable contacts carried by said armatu e at opposite sides of said pivotal connection, stationary contacts cooperating therewith, a single magnet, one end of said magnet attracting said armature at one point on one side of said pivotal connection to tend to hold one pair of contacts in engagement, the other end of said magnet attracting said armature at another point on the other side of said pivotal connection to tend to hold the other pair of contacts in engagement, one of said points being nearer said pivotal connection than the other, and stops limiting the movement of both ends of said armature away rem said magnet.

iii. In a device of the character described, a bimetallic element having a. fixed end and a free end, an armature carried by the free end of the element by means of a pivotal connection intermediate the ends of said armature, a pair of movable contacts carried by said armature at opposite sides of said pivotal connection, stationary contacts cooperating therewith, a channel shaped magnet extending lengthwise of and adjacent said armature to tend to hold said contacts in engagement, said pivotal connection being nearer one end of said magnet than the other, and means limiting the movement of each end of said armature away from said magnet.

14. In a device ofthe character described, a. bimetallic element having a fixed end and a free end, an armature carried by the free end of the element by means or a. pivotal connection intermediate the ends of said armature, a pair of movable contacts carried by said armatureat op posite side of said pivotal connection, stationary contacts cooperating therewith, a channel shaped magnet extending lengthwise of and adjacent said-armature to tend to hold said contacts in engagement, said pivotal connection being nearer one end of said magnet than the other, a pair of stops for limiting the movement of the ends of said armature away from said magnet,

one of said stops being carried by the bimetallic element, and means for moving the fixed end of said bimetallic element to vary the temperature at which said element willactuate said contacts;

CARL G. KRONMILLER. 

